Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 107,130	$ 53,714
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	108,205	104,095
Stock-based compensation	45,305	44,686
Provision (benefit) for deferred income taxes	8,982	(7,814)
Amortization of debt discount and issuance costs	11,618	4,850
Restructuring-related software charges	0	2,818
Other non-cash reconciling items, net	(121)	4,379
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(43,766)	(18,419)
Prepaid expenses and other current assets	(13,029)	(4,927)
Accounts payable and accrued expenses	(85,366)	(31,312)
Deferred revenue	29,286	25,243
Other current liabilities	(9,473)	13,701
Other non-current assets and liabilities	2,079	996
Net cash provided by operating activities	160,850	192,010
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(121,464)	(79)
Cash paid for equity method investment	(40,213)	0
Purchases of property and equipment	(69,752)	(51,584)
Capitalization of internal-use software development costs	(72,677)	(61,491)
Purchases of short- and long-term marketable securities	(10,625)	(73,352)
Proceeds from sales of short- and long-term marketable securities	244	16,196
Proceeds from maturities of short- and long-term marketable securities	547,793	59,540
Other non-current assets and liabilities	2,935	(715)
Net cash provided by (used in) investing activities	236,241	(111,485)
Cash flows from financing activities:
Repayment of convertible senior notes	(690,000)	0
Proceeds related to the issuance of common stock under stock plans	19,774	22,738
Employee taxes paid related to net share settlement of stock-based awards	(38,639)	(29,714)
Repurchases of common stock	(34,872)	(19,785)
Other non-current assets and liabilities	(1,558)	(3,900)
Net cash used in financing activities	(745,295)	(30,661)
Effects of exchange rate changes on cash, cash equivalents and restricted cash	1,601	1,165
Net (decrease) increase in cash, cash equivalents and restricted cash	(346,603)	51,029
Cash, cash equivalents and restricted cash at beginning of period	1,036,987	314,429
Cash, cash equivalents and restricted cash at end of period	690,384	365,458
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received of $1,176 and $4,476 for the three months ended March 31, 2019 and 2018, respectively	44,165	18,313
Cash paid for operating lease liabilities	30,504
Non-cash activities:
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	29,257
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	49,627	18,555
Capitalization of stock-based compensation	$ 8,831	$ 7,811